Control apparatus



Sept. 19, 1961 1 P, ENTIN 3,000,221

CONTROL APPARATUS Filed May 25, 1959 u n N INVENTOR. LEONARD E ENT|N ATTORN EY OUTPUT 3 0 United States .Patent i) 3,000,221 s CONTROL APPARATUS Leonard' P. Entin, Wayland, Mass., assignor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware l Filed May 2S, 1959. Ser. No. 815,373

7 Claims. (Cl. 73-517) air -frame angular motions are not imparted thereto. 111-- a strapped-down system the accelerometers must partake o f severe air frame angularmotions.- Inthe prior artvmulti-axis accelerometers the centroids of the respective `seismic masses are not space-coincident. According'ly,.for these prior art devices air frame angular motio'ns willfappear to be linear acceleration inputs and accordingly there will be outputs from the accelerometers indicativeof this. [hese are false signals or error signalswhich'are identiiied as separation errors.

The present invention overcomes the shortcomings of the'prior art multi-axisV accelerometer packages by providng a unique conguration which permits the mass centroids of the individual seismic masses to coincide substantially at a single point in space, at least for one of input acceleration conditionsg meiitheretofore not accomplished by the prior art devices andl renders the lpresent apparatus substantially free from thefsepa'ration'error problem.V

It is'an object of the present invention therefore to provideanimproved control apparatus. l

Affurther object of the invention is to provide an improved multi-axis acceleration sensor which is substantially immune from the separation error problem.

'Iliese and other objects of the invention will be set forth more fully and will become apparent from a reading of the following specification and appended claims, in,co`njunction with the accompanying drawing in which is disclosed a three-axis accelerometer in perspective view,

portions of .which have been omitted to facilitate a clear-` explanation ofthe invention.`v

ln the drawing the reference numeral 10 generally depicts a three-axis accelerometer comprising in part a base means 12 which is only schematically represented byfthe conventionally used symbol. In the drawing a This is an achieveset'of orthogonally arranged axes is depicted. 'Ihese are shown by way of example'to pitch,`roll and yaw axes 16', 18', and 20 craft.

The three-axis accelerometer comprises three separate linear accelerometers, one adapted to sense acceleration for example along the roll axis 16', one to sense acceleration for example along the yaw axis 20', and one adapted toy sense acceleration for example along the pitch axis 18'.. .In other words, linear4 accelerometers are mutually perpendicular.

of a dirigible l'Each of the individuallinear accelerometersl comprises a generally elongated member or rod-like mass element. The rod-like element for the roll axis accelerometer is identied by reference numeral 16, that for the pitch axis accelerometer by reference numeral 18, and that for the yaw axis accelerometer by the reference numeral 20. The rod-like elements 16, 18 and 20 have longitudinal axescoincident with the roll, pitch, andA yaw axes 16',

depict respectively the thelinput axes of the individual "ice,

18', and 20 respectively and each is individually mounted by suitable means for longitudinal movement relative to the base means 12. The present invention contem- The diaphragms supporting the rod-like element 16 are identified by reference numerals 21 and 22, those for' the rod-like element 18 by the reference numerals 23 and' 24, and those for the rod-like element 20 by the reference numerals 25 and 26. As shown the diaphragms -arc secured at their outer peripheries to the base means 12` andare secured at their inner portions by suitable means not shown specifically to the rod-like elements 16, 18 and 20. Thus the diaphragrns 21-26 provide a'means forsupporting the individual rod-like elements for lonf gitudinal motion relative to the base means 12.

At least two of the rod-like elements -16, 18, and 20,l f are characterized by having their central' portions odset somewhat from the longitudinal axes thereof. As de.'

picted the rod-like elements 16 and 18 have their central portions so modified. More specically the rod-like element 16 has its central portion Vodset in a W-like con" guration generally identied by the reference numeral central portion odl,

30 and the rod-like element 18 has its set into al W-like configuration identiedby reference numeral 32. As depicted the rod-like element 20 'has' a "l straight central portion. The signidcance of these odset; 1 portions 30 and 32 for the rod-likeelements .16* and 18 '.L will be appreciated when it is understood'thatby. having l 16, 18 and 20 may be orthogonally arl ranged with themass centroids of the individual ele-" ments 16, 18 and 20 all coinciding at substantially themv This point of coincidence of the mass centroids is identified in the drawing by the reference nu-jj. meral 34. Thus the combination of the odset portions 1 30 'and 32 of the elements 16 and 18 with the mounting them the elements same point.

Ymeans which Orients the three elements 16, 1,8 and 20 orthogonally permits the three rod-like elements to be mounted so that their longitudinal axes substantially in-" tersect and so that their mass centroids substantially coincide. With this configuration the device is substantially immune from separation errors.

The odset portions 30 and 32 as indicated have a W- This is one of various congurations that may be used according to the teaching of the :v v invention so as to permit the mass centroids of'elements like conguration.

16, 18, and 20 to lie (at least for one set of input acceleraportion of the to the base means in response to input accelerations. As

will be explained below, the actual longitudinal excur- -sions of the seismic elements may be kept relatively low by proper design.

Means for producing a signal indicative of relative movement between the individual accelerometers and?- the base means 12 may be provided. Such means are i only shown on the drawing as applied to theroll axisv acceleration sensor but it will be understood that simii lar means would be provided for the other two accelerometers, these means being omitted from the drawing so as to simplify the presentation.Y Any suitable type of signal producing means may be provided. As shown, the

.Panarea sept. .19, 1.961

`A. a,... A

signalgenerating means for the roll axis accelerometer is depictedas yan induction pickoff'generally identified `by the reference numeral 40 andwhich comprises a stator element 42 adapted to`be secured tothe baseV means 127,.

byjsnitable means and an armature element 44 radapted to beintegrally attached tothe rod-like element 16. The stator element 42has vsuitable winding means 45 not shown'in detail. Such winding means would hecharacterized byhaving` rst windings adapted to be ener-y gizedby. anV energizing; signal andto have additional windings adapted to be pick-upwindings Iwhich would have induced therein control voltages of a phase and.

magnitudeindicative of the sense and' magnitude .of relativeV movement between the rod-like element 16 and the base 12. The output .from the inductive pickoii` 40`is provided at a pair of terminals to which is connected a lead member 47.

There may also be associated with Veach of the individual linear accelerometers a force producing ymeans vfor causing relative motionY between the rod-likeyelementsand the base l2jupon a suitable.cornmandlsignal.

A typical force producingmeansuis depicted in the drawing in connection withgthe rollhaxisraccelerometer in.- cluding the rod-like -element v16 and fit will be understood that .similar meansA maybe providedvifgdesired fof ,bothw ofthe otherv accelerometers, namely the yaw axis ac- 4 celerometer. includingthelrod-lik'e element (2Q andthe pitch axis accelerometer,includingtherod-like element 18. Such` additional force producing means are not de',-`

picted vsolas tOsimplify thelpresentation. Theforce produng means vforthe roll axismaccelerometer including the rod-likeelement. 16 may generally be of any suitable type, the fmeans depicted` being generally the .type

off structure shown in the` cogpending application, f-

Leonardy P2 Eutinu andY AlanM. Campbell, Serial lNo. 771,994, tiled November 5, 19.58. This force producing means is generally identiedby referencenumeral S0 and i comprises a, st ator element.52 having a plurality ofiinwardly extendinglpoleportons 53.uponvwhich suitable winding means, not showmwouldV be provided. The

force producngmeans 50 also includes an .armature element 54 which is connected to anextension 55 of the tothegbase 12, This signal is adapted to be connected.

to ,ardisplacement amplifier 60 and to a diierentiating meansl. The `output from the differentiating means 61 would be-a signal indicative of the rate of change oflthevdisplacement, signaland is applied through a lead 62 to a rateaampliiier; 63. The outputs of the displacement amplierand rate amplier 60 and 63 are fed respectively throughsuitable leads 64 and 65 to suitablefdemodulatormeans V66V and V67. TheY outputs of the demodulators 66 and 67 arelapplied tothe force producingvmeans 50 lthrough* a suitable lead 68. It will berrnnderstood that lthe speciiic details of the means connecting the signal producing means 40 to the force producing means 50 have -been omitted for. simplicity sincelthey tornino speciclpart, of the invention. Any suitablemeanslmay be provided for these various elemQDS- Also it should be yunderstood that the Yteaching of the.

invention may be Vapplied to accelerometers of the open loop type Where mechanically resilient means would be providedto A'bias the seismic elements 16, 18 and 20 to nullf'signal p roducingpositions. Anexample of an open In operation; the three axis vacvzcelerometer 1Q serves to sense accelerations along three orthogonal axes or in other,

words along A,three axesmutually perpendicular and. Passing throughthe same point, The present invention pro-l vides a unique conguration as described above so that the mass centroids ottheindivdual ,linear accelerometersf may allwcoinideatthe same point in space, at least'vfor oneset of input acceleration conditions. For lpulposeliV of understanding the invention vbetter an acoflerationv along the r-ol1 ax.is .16'.may be assumedso as to cause .relative-movementbetween the rod-like element 16.21141 the baselz. The diaphragms 2.1. .and .2.2 suimortirietherod-V iike Velementinperinit the element 16 to mpveiongizmait nally relativeftofthebase 12.1 This relative movement will Ycause Aa relative movement .between the .armature .44 and the stator 42 ofvtllesignalproducing meano. This..

producesv aiarlal 0f a.phase and. maenitudeindicative of the sense andA magnitndeof orignalrelatve movement. between the-rodv-likeelement 16 andthe base -1 42 ThisV sgnalisappliedfto thedisplacement.amplifier. 60 and also through;the.rdiierentiatnglmeans 6,1 Ato the rate-iam: pliierls. The outputsfrpmthe amplers .are demodu:

lated 4by. demodulators 66and 67 'andas indicated-are applied to the aforceproducing means. The sense .oi energizatonot theaforce producing .means .50 issu l1,A

that the'armature Yelement54 willtransmtto .the rod-like.

element ,164Y a force tending to opposethe initial. force.

which causes the relative movement betweenme elementsy 16vand the .base 12.... Thusgtherelis provided@ .forcerebalance mode of operation for thelaccelerotneter.` By

using this-fclosedloop? type -of, operation the actualjexcursionof the mass .centroid ofthe individual rod-'like elementaway from its neutral position may be kept very low. Further, vthe amount ofy signal applied to the force producingmeans 50 is indicative of the actual acceleration sensed byvtheindividual linear ac celerometer. This signal tothe force-producing means may be measured at a suitable output terminal 70 for usein additional .COIllOl apparatuanot shown.

As explained above if desiredeach of the indiyidua'lj linear Vaccelerometerswould have Vsignal.producing means and if desired forcel producingmeans aSSOCiated Vwithlritl v so asto provide the same functions asis-depicted in connection with theV accelerometery including Vthe rod-'like l element 16,.V Itrwill rbe understood that rthethreefaxi's, accelerometer package generally .identified by thereference numeral 10 maysimultaneously senseaccelerations along. three orthogonal axes which may be the pitch, roll; and yaw axesof a vdirigible. Craft. Dile tothe uniqueoset' arrangement inthecentral portions of at least two of the linear .accelerometers the mass centroids may all'be oriented so asto coincide at the single point 34 in space.V

Inv some modes ofroperationit may be desired only to sense 'accelerations inwtwo axes. Inthis case oulytwo linear accelerometers are needed, `one of which may have a straight shank. portion .while the otherwould :have an oiisetption Aso that the .massentroids wouldalso coincide .at thesame .pointin space.

While lI have shown and .describedla specific embodiment of my invention, further modifications and improve- -ments will occur to those skilled in the art. Y I desire it to be understood, therefore, that this invention is not 'limited to the particular form shown and I intendin the appelidel.fl

claims to cover all modications which do not depart from the spirit and scope of this invention.

What I claim is:

1. Apparatus for sensing accelerations along tirst, second, and third mutually perpendicular intersecting axes, said apparatus comprising: base means; three rod-like members each having a longitudinal axis and at least two of which have otiset central portions; means for mounting said members orthogonally on said base means for movement relative thereto, said mounting means positioning said members so that the longitudinal axes thereof are respectively substantially coincident with said first, second, and third mutually perpendicular intersecting axes, so that said oiset central portions are separated from one another and so that the mass centroids of said members coincide at substantially the same point for at least one set of input acceleration conditions; pickofE means associated with each member for producing a signal indicative of relative movement between its member and said base; force producing means associated with each member adapted when actuated to cause movement between its member and said base; and means connecting the pickoi means and the force producing means associated with each member.

2. Apparatus for sensing accelerations along rst, second, and third mutually perpendicular intersecting axes, said apparatus comprising: base means; three rod-like mass members each having a longitudinal axis and at fleast two of which have otset central portions; means for individually mounting said mass members orthogonally on said base means for movement relative thereto, said offset portion permitting said mounting means to position said members so that the longitudinal axes thereof are respectively substantially coincident with said rst, second, and third mutually perpendicular intersecting axes, and so that the mass centroids of said mass members coincide at substantially the same point for at :least one set of input acceleration conditions; pickoi means associated with each mass member for producing a signal indicative of relative movement between its member and said base; force producing means associated with each mass member adapted when actuated to cause movement between its member and said base; and means connecting the pickoii means and the force producing means associated with each mass member.

3. Apparatus for sensing accelerations along iirst and second mutually perpendicular intersecting axes, said apparatus comprising: base means: first and second rod-like members each having a longitudinal axis and at least one of which has an offset central portion; means for mounting said members on said base means for longitudinal movement relative thereto, said offset portion permitting said mounting means to position said members so that the longitudinal axes thereof are respectively substantially coincident with said rst and second perpendicular intersecting axes, so that said members are separated from one another, and so that the mass centroids of said members coincide at substantially the same point for at least one set of input acceleration conditions; pickol means associated with each member for producing a signal indicative of relative movement between its member and said base; force producing means associated with each member adapted when actuated to cause movement between its member and said base; and means connecting the pickoii means and the force producing means associated with each member.

4. Apparatus for sensing accelerations along rst and second perpendicular intersecting axes, said apparatus comprising: base means; first and second mass members each having a longitudinal axis and at least one of which has an oiiset central portion; and means for individually mounting said mass members on said base means for longitudinal movement relative thereto, said otset portion permitting said mounting means to position said mass members so that the longitudinal axes thereof are respectively substantially coincident with said first land second perpendicular intersecting axes, and so that the mass centroids of said mass members coincide at substantially the same point for at least one set of input acceleration conditions.

5. In a multi-axis accelerometer: a base, three elongated members, at least two of which have central portions thereof oiset from their respective longitudinal axes, and each of said members being characterized by its mass centroid lying substantially on its longitudinal axis; mounting means for each member for individually mounting said members for movement relative to said base along their respective longitudinal axes, said offset portions permitting said mounting means to position said members orthogonally relative to one another and so that said mass centroids of said members substantially coincide; and pickot means associated with each member for producing a signal indicative of relative movement between each of said members and said base.

6. Apparatus for sensing accelerations along rst and second perpendicular intersecting axes comprising: base means; first and second elongated members each having a longitudinal axis; means for individually mounting said members on said base means so that the longitudinal axes of said members are respectively substantially coincident with said intersecting axes and so that the mass centroids of said members substantially coincide for one set of input acceleration conditions.

7. Apparatus for sensing accelerations along rst and second intersecting axes comprising: base means; rst and second members each having an axis passing through the mass centroid thereof; means for individually mount- -ing said members on said base means so that said axes thereof are respectively substantially coincident with said intersecting axes and so that said mass centroids substantrally corncide for one set of input acceleration conditions.

References Cited in the le of this patent UNITED STATES PATENTS 2,570,672 Hathaway Oct. 9, 1951 2,695,165 Hansen Nov. 23, 1954 2,856,240 Breazeale et al. Oct. 14, 1958 

